Interesting post, Chuck. But the need for grid storage and the requisite infrastructure to support it seems to me to have the same limitations and issues as the charging infrastructure dilemma you've been writing about lately with EVs. Building out the grid storage will take money and physical space, correct? I'm imaging it like giant data centers all over the place, so please set me straight. Will this be funded by private industry, the government? And without it, what happens to the use of renewable energy--it hits a brick wall.

The opposite side of this is manipulating the demand side. Some utilities are now pushing 'smart' meters and appliances that will give the utility the option of reducing your consumption at peak load times. That may influence some customers to install small at-home back-up systems. Right now the savings are not enough for me to give the utility control over my appliances. And I don't think a UPS can be had for the saving offered either. Plus there would be the difficulty of how to wire / control such a system.

Beth, it's not as bad as all that. By using grid storage utilities can avoid building or upgrading other generation capacity. Thus, it may not be a big extra expense in the long run. In addition, this technology offers a way to make the grid more reliable. I have seen plans for batteries at the substation level. We'll have to see how the battery technology pans out.

Beth, I should have been more emphatic in stating that this is about the demand, not about what will actually happen. Lux's study is looking at plans, such as those in California (which wants to boost its renewables over 30%) and saying, "here's what will be needed." You're correct on all counts: yes, construction of these facilities will take money (public or private) and, yes, these storage centers will be very large. As for whether renewables will hit a brick wall without it: Yes, they will. The question is, when? Today, wind and solar generate about 4-6% of our electrical capacity. Experts at Argonne National Laboratory say that we will need storage when we reach a point between 10% and 20%.

Thanks for clarifying, Chuck. So we have some time to build out the grid storage and Naperlou talks about how it can be accomplished pretty effectively. I am by no means trying to poke holes in this development. As with all of this alternative fuel and renewable energy technology, it's a process and it's going to take time, money, and innovations in order to pull us over the goal line.

The Lux report does indeed reinforce the need for large-scale energy storage solutions as renewable energy deployments continue. Other researchers (Pike, Frost and Sullivan, EPRI) have reported much the same thing. The only two proven viable (efficient and economic) methods thus far for storing hundreds of MW for hours - pumped hydro and compressed air energy storage, or CAES - have not seen wider implementation due to geological, environmental and capital constraints. Indeed, no CAES system has been built for more than 20 years (and there are only two in the world).

A new method for compressing large volumes of air to store energy at low cost exists and is being developed by several companies, my own included. Isothermal CAES compresses air but does so in a way that maintains near-constant temperature, thus avoiding the inefficiencies of conventional CAES. ICAES also allows site-anywhere storage using pipes, rather than relying on caverns. Even better, because it retains most of the heat produced during compression, ICAES does not need a natural gas turbine to reheat the air during decompression, thus avoiding emissions and fossil fuel consumption. It's a truly sustainable solution that will be deployed on a MW scale in 2013.

One note about Lux's reference to flywheels: they are not considered a bulk storage technology and are not able to provide MWs for hours as is needed for diurnal renewable energy storage. Flywheels are fast-responding devices that are very good at delivering short bursts of energy for minutes (and absorbing the same), in order to provide grid ancillary services like frequency regulation. This is considered a power application, where the demands to inject or absorb energy are instantaneous and durations relatively brief, but with many cycles each day. As renewable use expands and brings all of its intermittencies with it, short-duration fast-response storage systems will also be needed to smooth out the irregularities and maintain stability. But they will not compete with ICAES, large battery systems, or other emerging methods of providing bulk storage.

Rob, pumped hydro (i.e., the lake on the hill) is still our biggest source of storage today. But as commenter ehunt has so succinctly stated below, pumped hydro "has not seen wider implementation due to geological, environmental and capital constraints."

I can understand that, Chuck. I'm curious, though, as to the economic feasibility of pumped hydro compared with alternatives. I would think that once the lake is in place, the system for pumping and retrieving power via that downhill stream would be relatively inexpensive. As for the lake -- seems every community could stand an extra lake.

I don't know about the economic feasibility of pumped hydro versus batteries, Rob, largely because so much of pumped hydro's cost is dependent on the price of the land. In terms of system technology, pumped hydro has a big advantage over the acres of batteries that would otherwise be used (and would later need to be replaced). But for pumped hydro, it's always going to come back to land availability and cost.

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